Systems and methods for configuring redundant transmissions in a wireless network

ABSTRACT

A method for configuring communication in a wireless communication system includes obtaining, at a first network node, information indicating a plurality of candidate subframes for downlink transmissions to a wireless communication device in a first cell served by the first network node. Each candidate subframe satisfies a candidate condition that relates to transmissions in a second cell during that subframe. The method also includes determining, based on the obtained information, a number of copies of an uplink transmission a wireless communication device should transmit in consecutive uplink subframes so that a downlink transmission related to the uplink transmission will occur during one of the candidate subframes. Additionally, the method includes configuring the wireless communication device to transmit the determined number of copies of the uplink transmission in consecutive subframes.

TECHNICAL FIELD OF THE INVENTION

This disclosure relates in general to wireless communication and, moreparticularly, to improving the reliability of wireless transmissions.

BACKGROUND OF THE INVENTION

The dramatic increase in the use and availability of communicationservices in recent years has placed significantly greater demands onwireless communication networks. Continually increasing requirements forcoverage, throughput, and reliability have driven many developments inthe design and configuration of wireless networks. One example of thishas been the development of “heterogeneous” networks in whichconventional macro-cell base stations are supplemented by the deploymentof various types of “low-power” nodes that provide lower maximumtransmission power levels than conventional macro-cell base stations.These low-power nodes are often smaller and cheaper, both to manufactureand to operate, than conventional macro-cell access nodes.

Heterogeneous deployments provide a mechanism for increasing networkdensities and for adapting to changes in traffic needs and operatingenvironment. However, heterogeneous deployments bring unique challengesthat may hinder efficient network operation and degrade user experience.The reduced transmission power typically associated with low-power nodescan result in an increased sensitivity to interference. Additionally,the mix of large and small cells in a heterogeneous deployment can leadto other challenges, as a result of the asymmetric power capabilities ofthe different cells. As a result, there is a need for effectivesolutions to reduce inter-cell interference in heterogeneous deploymentsand other advanced networks.

SUMMARY OF THE INVENTION

In accordance with the present disclosure, certain disadvantages andproblems associated with wireless communication have been substantiallyreduced or eliminated. In particular, certain devices and techniques forproviding wireless telecommunication service are described.

In accordance with one embodiment of the present disclosure, a method ofconfiguring communication in a wireless communication system includesobtaining, at a first network node, information indicating a pluralityof candidate subframes for downlink transmissions to a wirelesscommunication device in a first cell served by the first network node.Each candidate subframe satisfies a candidate condition that relates totransmissions in a second cell during that subframe. The method alsoincludes determining, based on the obtained information, a number ofcopies of an uplink transmission a wireless communication device shouldtransmit in consecutive uplink subframes so that a downlink transmissionrelated to the uplink transmission will occur during one of thecandidate subframes. Additionally, the method includes configuring thewireless communication device to transmit the determined number ofcopies of the uplink transmission in consecutive subframes.

In accordance with another embodiment of the present disclosure, amethod of configuring communication in a wireless communication systemincludes obtaining information indicating a first group of one or moresubframes of a radio frame in which a first network node will transmitfeedback information to one or more wireless communication devicesserved by the first network node. The method also includes determining,based on the obtained information, a second group of one or moresubframes in which a second network node should transmit feedbackinformation to one or more wireless communication devices served by thesecond network node. The second group of subframes differs from thefirst group of subframes. The method additionally includes configuringthe second network node to transmit feedback information to one or morewireless communication devices during the second group of subframes andtransmitting feedback information from the first network node during thesecond group of subframes.

Important technical advantages provided by certain embodiments of thepresent disclosure include improved reliability in wirelesscommunications. Particular embodiments may be capable of reducinginter-cell interference experienced by wireless communication devices,especially in heterogeneous networks. Such embodiments may be capable ofreducing the number of erroneous transmissions and/or increasing thelikelihood that wireless transmissions will be successfully received.Additionally, in particular embodiments, the reduction in interferencecan be achieved with minimal impact on the throughput of the interferingcell. Other advantages of the present invention will be readily apparentto one skilled in the art from the following figures, descriptions, andclaims. Moreover, while specific advantages have been enumerated above,various embodiments may include all, some, or none of the enumeratedadvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsadvantages, reference is now made to the following description, taken inconjunction with the accompanying drawings, in which:

FIGS. 1A-1C illustrate particular embodiments of a wirelesscommunication system in which the described solutions may beimplemented;

FIGS. 2A and 2B illustrate example transmission patterns for a subframeconfigured as, respectively, a Multicast and Broadcast Single FrequencyNetwork (MBSFN) Almost Blank Subframe (ABS) subframe and a non-MBSFN ABSsubframe;

FIG. 3 is a diagram showing possible MBSFN-configurable subframesaccording to an example frame configuration;

FIG. 4 illustrates example timing for certain downlink transmissionsrelative to a set of candidate subframes that may be used to protectdownlink transmissions;

FIGS. 5A and 5B illustrate example timing for Hybrid-Automatic RepeatreQuest (HARQ) transmissions under various scenarios;

FIG. 6 illustrates another example of the relative timing of thedownlink transmissions and candidate subframes from FIG. 4 when multiplecopies of a related uplink transmission are made;

FIG. 7 is a flow chart showing example operation of a particularembodiment of a radio access network node in facilitating the protectionof downlink transmissions;

FIG. 8 illustrates another embodiment of the example wirelesscommunication system from FIGS. 1A-1C in which radio access networknodes coordinate their operation to provide protection for downlinktransmissions;

FIG. 9 is a flow chart showing example operation of a particularembodiment of a radio access node in coordinating with another radioaccess node to protect downlink transmissions; and

FIG. 10 is a block diagram illustrating the contents of an exampleembodiment of a radio access node that may be utilized in particularembodiments of the wireless communication system.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1A illustrates a wireless communication system 10 that providescommunication service to one or more wireless communication devices 20.Wireless communication system 10 includes an access network 30 thatprovides wireless access to communication services within a particulargeographic area and a core network 40 that provides backhaul delivery ofinformation within wireless communication system 10. Access network 30includes multiple radio access nodes including, in certain embodiments,multiple different types of radio access nodes (e.g., both base stations32 and low-power nodes 34). Each radio access node serves one or morecells 50. Because of the close proximity (and potential overlap) of thecells 50, a wireless communication device 20 operating in a first cell50 (referred to herein as a “victim cell”) may suffer interference dueto transmissions occurring in a second cell 50 (referred to herein as an“aggressor cell”) that is overlapping or near to the victim cell. Thisaggressor cell may be served by the same radio access node as the victimcell or by a different radio access node.

Additionally, as noted above, access network 30 may represent aheterogeneous network in which radio access nodes transmitting atdifferent power levels are deployed. This may create more severeinterference problems, especially when the victim cell is served by aradio access node using a higher power than the radio access nodeserving the interfering cell—e.g., for FIG. 1A, in situations in whichthe victim cell is served by one of low-power nodes 34 and the aggressorcell is served by one of base stations 32.

These interference problems may be even further exacerbated by certainsolutions that are commonly implemented in heterogeneous networks thatutilize certain types of low-power nodes 34. For example, FIG. 1Billustrates problems that may arise in certain embodiments of wirelesscommunication system 10 when one or more low-power nodes 34 areconfigured to utilize closed subscribed groups (CSGs). In the example ofFIG. 1B, one or more low-power nodes 34 are configured to utilize a CSG.The use of CSGs may allow low-power nodes 34 to limit access to theirservices to certain authorized users that are part of a “closedsubscriber group.” A radio access node configured with a CSG willprovide communication services to wireless communication devices 20 thatare members of the CSG, but deny service to wireless communicationdevices 20 that are not members of that node's CSG. For example, apicocell operated by an employer to provide service for its employees intheir workplace could be configured with a CSG that includes thewireless communication devices 20 of all the company's employees. Byusing the CSG, this low-power node 34 could provide additional or betterservice coverage to the company's employees beyond that provided bynearby base stations 32 but may still prevent non-employees in the areafrom tying up the picocell's transmission, reception, or processingresources.

Thus, non-CSG wireless communication devices 20 that are operating in acell 50 served by a CSG low-power node 34 cannot utilize CSG low-powernode 34, even though the CSG low-power node 34 may be the closest radioaccess node. On the other hand, wireless transmissions made by the CSGlow-power node 34 may still interfere with communications between thesenon-CSG wireless communication devices 20 and other radio access nodesserving them. Moreover, non-CSG wireless communication devices 20 may belocated extremely close to the CSG low-power node 34 despite beingunable to obtain service from the CSG low-power node 34, which mayresult in a significant amount of interference for the non-CSG wirelesscommunication devices 20. For instance, in the example shown in FIG. 1B,it is assumed that wireless communication device 20 g is not a member ofthe CSG served by low-power node 34 g and cannot obtain service fromlow-power node 34 g. Instead, wireless communication device 20 g isserved by base station 32 g in cell 50 j. As a result, cell 34 g servedby CSG low-power node 34 g may act as an aggressor cell while wirelesscommunication device 20 is operating in the portion of cell 50 j thatoverlaps cell 34 g. The interference from this aggressor cell 50 g maybe extremely high wireless communication device 20 g is operating veryclose to low-power node 34 g.

Another interference problem that may arise, especially in heterogeneousnetworks, relates to the use of “cell range expansion” (or “cell rangeextension”) (CRE) zones. FIG. 1C illustrates an example in which one ormore low-power nodes 34 are configured to support CREs. In CREs, cellselection/re-selection diverges from a conventionalsignal-strength-based (e.g., RSRP-based) approach towards, for example,a pathloss- or pathgain-based approach, thereby extending the coverageof the lower-power cell to include additional areas (represented by CREzones 52 in FIG. 1C). The larger a particular CRE zone 52 is, the weakerserving cell's signal strength will be near its boundary. This mayresult in nearby macro cells acting as aggressor cells to wirelesscommunication devices 20 operating in a CRE zone 52. For example, inFIG. 1C, cell 50 m served by base station 32 k may act as an aggressorcell for wireless communication device 20 k operating in CRE zone 52 kof low-power node 34 k. Thus, in general, as shown by FIGS. 1A-1Cinter-cell interference can be a significant concern in wirelesscommunication systems, particularly in those implementing heterogeneousdeployments.

It may be critical to protect certain types of signaling from suchinter-cell interference. For example, certain embodiments of wirelesscommunication system 10, such as those supporting LTE, may utilizeHybrid-Automatic Repeat reQuest (HARQ) functionalities for transmissionerror correction. In particular embodiments, HARQ functionality providesan N-process Stop-And-Wait mechanism that transmits and retransmitstransport blocks. Upon reception of a transport block, the receivermakes an attempt to decode the transport block and informs thetransmitter about the outcome of the decoding operation by transmittingfeedback information (e.g., a single-bit acknowledgement (ACK) forsuccessful reception or negative acknowledgement (NAK) for unsuccessfulreception) indicating whether the decoding was successful and/or whethera retransmission of the transport block is required. If interferencefrom an aggressor cell prevents feedback information of this type frombeing successfully transmitted, a significant number of unnecessaryretransmissions may occur and/or erroneously received transmissions maynever be retransmitted.

Additionally, HARQ may also be used for contention-based random accesstransmissions, both for a first scheduled uplink transmission (e.g., forinitial access, after handover, or upon RRC connection reestablishment)and for contention resolution in downlink (where HARQ feedback istransmitted only by the wireless communication device 20 which detectsits own identity, as provided in message 3, echoed in a ContentionResolution message). HARQ failure in the first uplink transmission stepor in the contention resolution step may result, for example, in a cellradio network temporary identity (C-RNTI) detection failure by therelevant wireless communication device 20 or erroneous assignment of thesame C-RNTI also to another wireless communication device 20.

Certain embodiments of wireless communication system 10 utilize“synchronous HARQ” for some or all of their transmissions. For example,LTE implementations use synchronous HARQ for uplink user datatransmissions on the Uplink Shared CHannel (UL-SCH), providing HARQfeedback information in the downlink on a Physical Hybrid-ARQ IndicatorCHannel (PHICH). Synchronous HARQ involves synchronous HARQ feedback andsynchronous retransmissions. In such embodiments, the time instants fordownlink transmissions of feedback information and any uplinkretransmissions are fixed based on the subframe(s) scheduled for theuplink transmissions and known to both the radio access node and therelevant wireless communication device 20. Consequently, there may notbe any need to signal a HARQ process number when operating in this HARQmode. The maximum number of retransmissions may be configured perwireless communication device 20. An example of synchronous HARQoperation is shown in FIG. 5A.

In particular embodiments of wireless communication system 10,transmissions in aggressor cells may be constrained by predeterminedtransmission patterns that limit downlink transmissions made by theradio access nodes serving those cells. These transmission patterns maylimit the time and/or frequency resources that are used for makingdownlink transmissions in the relevant cell. As a result, thesetransmission patterns may provide a victim cell protection frominterference by an aggressor cell in other time and/or frequencyresources.

For example, wireless communication system 10 may configure radio accessnodes to utilize Almost Blank Subframe (ABS) patterns that result inthese radio access nodes transmitting a minimal amount of signalingduring certain subframes. In particular embodiments, ABS patterns definelow-power and/or low-transmission activity subframes (e.g., subframes inwhich a reduced number of modulation symbols are transmitted or someother reduction in the amount of data or signaling occurs) for therelevant cell 50. For example, an ABS pattern for a potential aggressorcell may specify a number of subframes during which no user data istransmitted in the aggressor cell, although control channel informationmay still be transmitted during the relevant subframes. In particularembodiments, ABS patterns may be exchanged between radio access nodes(e.g., via an X2 interface).

Furthermore, in particular embodiments, the inter-cell interferencecaused by an aggressor cell may be significantly reduced during thoseABS subframes that are also configured as Multicast and Broadcast SingleFrequency Network (MBSFN) subframes. In certain embodiments, MBSFNsubframes are divided into a non-MBSFN region and an MBSFN region. Forexample, the non-MBSFN region may span the first one or two orthogonalfrequency division multiplexing (OFDM) symbols in an MBSFN subframe withthe length of the non-MBSFN region being 1 or 2 symbols (e.g., onesymbol may be used with 1 or 2 cell-specific ports when the number of DLresource blocks exceeds 10). In such embodiments, the MBSFN region in anMBSFN subframe may then be defined as the OFDM symbols that do not makeup part of the non-MBSFN region. While some MBSFN subframes may carrymulticast transmissions, such as Physical Multicast Channel (PMCH)transmission, not all MBSFN subframes include such transmissions,despite their name. MBSFN subframes without multicast transmissions arereferred to herein as “blank MBSFN subframes.”

Nonetheless, even in blank MBSFN subframes, certain types of signalingmay still be transmitted in part of the non-MBSFN region. For example,in LTE networks, common reference signals (CRS) may still be transmittedin the non-MBSFN region of the of blank MBSFN subframes, namely in thefirst symbol. However, unlike ABS configured in non-MBSFN subframes (a“non-MBSFN ABS configuration”), ABS configured in blank MBSFN subframes(an “MBSFN ABS configuration”) may result in less inter-cellinterference due to the fact that certain information (e.g., CRS in LTEnetworks) is not transmitted in the MBSFN region of MBSFN subframes. Asubframe diagram for an example MBSFN ABS configuration that may be usedin particular embodiments of wireless communication system 10 isschematically illustrated in FIG. 2A, while a subframe diagram for anexample non-MBSFN ABS configuration that may be used in particularembodiments is schematically illustrated in FIG. 2B. In the examples ofFIGS. 2A and 2B, it is assumed that two transmit antenna ports are usedfor CRS with transmissions shown for the first port (marked with “R0”)and the second port (marked with crosshatching). As can be seen fromFIGS. 2A and 2B, when a potential aggressor cell is configured withMBSFN ABS, transmissions will occur in fewer symbols per subframe thanwith non-MBSFN ABS, resulting in less overall interference from anaggressor cell configured with MBSFN ABS.

However, not all downlink (DL) subframes may be MBSFN-configurable. FIG.3 shows an example of how MBSFN configuration is constrained under the3GPP TS 36.331 specification for Long Term Evolution (LTE) networks whenFDD is utilized. As shown in FIG. 3, MBSFN cannot be configured insubframes #0, #4, #5, #9 in an FDD system, since some system informationmay need to be transmitted in these subframes. Thus, in suchembodiments, only subframes #1, #2, #3, #6, #7, and #8 can be configuredas MBSFN subframes. By contrast to the FDD constraints shown in FIG. 3,in TDD LTE systems, only subframes #3, #4, #7, #8, and #9 can beconfigured for MBSFN. While it might be possible to use a mixture ofMBSFN and non-MBSFN ABS to protect more subframes, mixing MBSFN andnon-MBSFN ABS subframes can produce other problems, such as inaccuratecell state information reports, less efficient demodulation algorithmsfor wireless communication devices 20 with advanced receivers,unnecessary constraints on network configuration, and reduced throughputin the aggressor cell. Additionally, some of the available MBSFNsubframes may need to be used for purposes other than interferencecancellation. Thus, wireless communication system 10 may not have enoughMBSFN cells available for ABS to protect all the downlink subframes inthe victim cell that it is necessary or desirable to protect. This meansthat MBSFN subframes can only be used to reduce interference at certaintimes and, in particular embodiments, the time periods that can beprotected may change from network to network.

Thus, constraints on how aggressor cell transmission patterns can beconfigured may make it impossible to protect all the necessarytransmission resources in the victim cell from interference using atransmission pattern such as an MBSFN ABS pattern. For example, assumethe HARQ timing in a particular embodiment of wireless communicationsystem 10 is based on an 8 ms periodicity, which is consistent with theHARQ periodicity set for LTE. If an uplink grant is first allocated insubframe n, HARQ feedback information (e.g., an ACK/NAK indication) willbe sent on the PHICH channel of subframes (n+8k) mod(10), where k is anypositive integer value and mod(.) is the modulus after division. When nis an odd number, Subframes 1, 9, 7, 5, and 3 will have ACK/NAKinformation for the corresponding HARQ process. In this case, althoughSubframe 9 and 5 would need protection, these subframes would notMBSFN-configurable in the example illustrated by FIG. 3. When n is aneven number, downlink HARQ feedback information will be transmitted inSubframes 0, 8, 6, 4, and 2 for the corresponding HARQ process. In thiscase, Subframes 0 and 4 need protection, but are not MBSFN-configurableeither under the example of FIG. 3.

To illustrate how this may cause problems, FIG. 4 shows an example ofthe uplink HARQ timing that may occur in an example embodiment ofwireless communication system 10 in which a radio access node isattempting to successfully transmit HARQ feedback on a PHCIH in a victimcell. It may be necessary to protect the PHICH transmission in thevictim cell with MBSFN ABS subframes or some other mechanism in theaggressor cell if a wireless communication device 20 in the victim cellis going to have any chance of successfully receiving and decoding thePHICH transmissions. In the example of FIG. 4, the subframes in a victimcell that require protection by MBSFN ABS subframes in the aggressorcell are shown in the row labeled “SF to be protected.” As FIG. 4illustrates, under this example configuration, Subframe 9 of Radio Frame0 and Subframe 5 of Radio Frame 2 cannot be protected with MBSFN ABSsubframe, since MBSFN cannot be configured in these subframes in thisexample. Consequently, only some of the resulting PHICH transmissionscan be protected by MBSFN ABS subframes, and without more, some PHICHtransmissions will not be detected reliably due to the configurationconstraints for MBSFN subframes.

This is an example of a more generic problem that may occur inparticular embodiments as a result of a mismatch in the periodicity ofthe relevant downlink transmissions (e.g., HARQ feedback informationtransmitted on PHCIH) and that of a transmission pattern (e.g., an MBSFNABS pattern) that provides appropriate interference conditions toprotect downlink transmissions in the victim cell. While it may bepossible to protect some of the downlink transmissions in a victim cellby simply taking advantage of a transmission pattern configured for theaggressor cell (e.g., an MBSFN ABS pattern), it may not be possible toprotect all downlink transmissions made in the victim cell in thismanner. In general, when there is a restriction (e.g., due to subframetype such as MBSFN/non-MBSFN, cyclic prefix configuration, interferenceconditions, network configuration, device activity state) on the timeand/or frequency resources that can be protected from interference bythe aggressor cell and at the same time there are pre-determined timeoccasions when certain downlink transmissions need to occur in thevictim cell (e.g., due to the timing constraints of synchronous HARQ),these pre-determined time occasions may not fully encompass all of thesubframes that could possibly be needed for downlink transmissions.Therefore, in embodiments of wireless communication system 10 thatexhibit a periodicity mismatch between a pattern of subframes that canbe interference-protected and the downlink transmissions that requiresuch protection, it may be impossible to protect all downlinktransmissions needing protection without additional measures beingtaken.

As a result, wireless communication system 10 is configured to controlthe time and/or frequency resources used for certain downlinktransmissions in a victim cell to ensure that the relevant downlinktransmissions coincide with a predefined, feasible subset of “candidate”resources that are or can be interference protected. More specifically,in particular embodiments of wireless communication system 10, a firstradio access node may be able to provide interference protection fordownlink transmissions in a first cell by exploiting transmissionpatterns in other cells. The first radio access node may configurecertain downlink transmissions on time and/or frequency resources thatwill experience no inter-cell interference or reduced levels ofinter-cell interference. As discussed further below in regards to FIGS.5A-5B, 6, and 7, one example of how radio access nodes can implementthis configuration is by utilizing redundant transmissions in certainuplink transmissions to beneficially adjust the timing of relateddownlink transmissions. In certain embodiments, radio access nodes invictim cells may implement the described configuration solutionsindependently, reacting to fixed transmissions patterns used by theaggressor cells. However, in alternative embodiments, radio access nodesin victim cells may instead be capable of interacting with radio accessnodes in potential aggressor cells to coordinate transmission patterns,as explained in further detail below with respect to FIGS. 8 and 9.

Returning now to the example embodiment shown in FIG. 1A, theillustrated embodiment of wireless communication system 10 provideswireless communication service to one or more wireless communicationdevices 20 operating within a plurality of cells 50 served by wirelesscommunication system 10. Wireless communication system 10 may supportcommunication of any suitable type and/or in accordance with anyappropriate communication standards including, but not limited to, anyLong Term Evolution (LTE), Worldwide Interoperability for MicrowaveAccess (WiMAX), and Wideband Code Division Multiple Access (WCDMA)communication standards.

Wireless communication device 20 represents any device capable ofcommunicating information wirelessly with wireless communication system10. Examples of wireless communication device 20 include traditionalcommunication devices such as wireless phones, personal digitalassistants (“PDAs”), laptop computers, and any other portablecommunication device suitable for use with communication system 10. Forexample, in particular embodiments, wireless communication device 20represents an instance of LTE user equipment (UE). Additionally, inparticular embodiments, wireless communication device 20 may alsorepresent automated equipment or devices capable of machine-typecommunication (MTC). For example, wireless communication device 20 mayrepresent a wireless meter or sensor, a digital billboard, awireless-capable appliance (e.g., a washing machine, furnace, digitalvideo recorder (DVR)), or any other device capable of wirelesscommunication with access network 30.

Access network 30 communicates wirelessly with wireless communicationdevices 20 and serves as an interface between wireless communicationdevices 20 and core network 40. Access network 30 may represent orinclude a radio access network and/or any elements responsible forproviding a radio or air interface for core network 40. Access network30 includes one or more radio access nodes capable of communicatingwirelessly with wireless communication devices 20. In the exampleembodiment of FIG. 1A, these radio access nodes include a plurality ofbase stations 32 and low-power nodes 34. Access network 30 may alsoinclude base station controllers, access servers, gateways, relays,repeaters, and/or any additional components suitable for managing radiochannels used by base station 32, authenticating users, controllinghandoffs between base station 32 and other radio access elements, and/orotherwise managing the interoperation of base stations 32 andinterfacing base stations 32 with core network 40.

In particular embodiments, access network 30 may represent aheterogeneous network in which multiple different types of radio accessnodes are deployed. For example, in the illustrated example of FIG. 1A,access network 30 includes a plurality of base stations 32 that eachserve one or more cells 50 and a plurality of low-power nodes 34 thateach serve one or more cells. For purposes of this description, cells 50served by base stations 32 are referred to as “macro” cells, while cells50 served by low-power stations 34 are referred to as “micro” cells. Inparticular embodiments, micro-cells served by low-power stations 34 maysubstantially overlap one or more macro-cells served by nearby basestations 32, as shown in FIG. 1A. Base stations 32 communicatewirelessly with wireless communication devices 20 to facilitate wirelesscommunication service for wireless communication devices 20. Basestations 32 may include any appropriate elements to communicate withwireless communication devices 20 and to interface wirelesscommunication devices 20 with core network 40. For example, depending onthe communications standards supported by access network 30 and corenetwork 40, each base station 32 may represent or include a basestation, a Node B, an evolved Node B (eNode B), a radio base station(RBS), or any other suitable element capable of communicating withwireless communication devices 20 wirelessly.

Similarly, low-power nodes 34 communicate wirelessly with wirelesscommunication devices 20 to facilitate wireless communication servicefor wireless communication devices 20. Low-power nodes 34 may alsoinclude any appropriate elements to communicate with wirelesscommunication devices 20 and to interface wireless communication devices20 with core network 40. In particular embodiments, low-power nodes 34may have a lower maximum transmission power than base stations 32, ormay be configured to use lower transmission powers than base stations32. Examples of low-power nodes 34 include, but are not limited to, picobase stations, femto base stations, micro base stations, home eNodeBs(HeNBs), and wireless local access network (WLAN) access points.

Although referred to as being “low-power,” low-power nodes 34 may, inparticular embodiments, include identical physical components to basestations 32 but, at a given time, may be simply configured to operatedifferently from base stations 32. Furthermore, although the descriptionbelow focuses, for purposes of example, on embodiments in which accessnetwork includes radio access nodes that differ in terms of transmissionpower, other embodiments of access network 30 may include differingtypes of radio access nodes that differ in regards to other aspects oftheir operations and/or other capabilities or characteristics. Moreover,alternative embodiments of access network 30 may represent homogeneousnetworks in which all of the radio access nodes are similar oridentical.

Each radio access node in access network 30 is associated with one ormore cells 50 that is served by that radio access node. Cells 50 maydefine an approximate geographical area served by the correspondingradio access node. For purposes of simplicity, FIG. 1A illustrates anexample embodiment in which each radio access node is configured toserve a single cell 50. However, in particular embodiments, the radioaccess nodes may be capable of supporting multiple different cells 50.For example, in embodiments that support carrier aggregation or othermulticarrier features, a particular radio access node may serve multipledifferent cells 50, possibly with identical geographic coverage, witheach of the cells 50 served by that radio access node using a carrierfrom a different portion of the frequency spectrum. As a result, inparticular embodiments, a first cell 50 and a second cell 50 may both beserved by the same radio access node, and those cells 50 may coveridentical, overlapping, or completely distinct geographical areas.

Core network 40 routes voice and/or data communicated by wirelesscommunication devices 20 from access network 30 to other wirelesscommunication devices 20 or to other communication devices coupled tocore network 40 through landline connections or through other networks.Core network 40 may support any appropriate standards or techniques forrouting such communications. For example, in embodiments of wirelesscommunication devices 20 that support LTE, core network 40 may representa System Architecture Evolution (SAE) core network. Core network 40 mayalso be responsible for aggregating communication for longhaultransmission, authenticating users, controlling calls, metering usagefor billing purposes, or other functionality associated with providingcommunication services. In general, however, core network 40 may includeany components suitable for routing and otherwise supporting voiceand/or data communications for wireless communication devices 20.

In operation, radio access nodes of wireless communication system 10(such as base stations 32 and low-power nodes 34 in the exampleembodiment) provide wireless communication service to wirelesscommunication devices 20 operating in the cells 50 served by these radioaccess nodes. To protect certain downlink transmissions from inter-cellinterference, the timing of these downlink transmissions is controlledto ensure that these transmissions occur in certain subframes (referredto herein as “candidate subframes”). These candidate subframes representsubframes in which one or more aggressor cells will have limited or notransmissions, overall interference in the victim cell will be reduced,and/or other desirable transmission conditions will occur for the victimcell.

For example, in particular embodiments, the candidate subframes mayrepresent those subframes, or a specific subset of those subframes, inwhich an aggressor cell is configured to transmit MBSFN ABS subframes.In particular embodiments, these candidate subframes may representsubframes in which transmissions by base station 32 a in the aggressorcell are limited in some way (e.g., the subframes configured as ABSsubframes under the ABS configuration), subframes in which low-powernode 34 a or access network 30 has designated as being acceptable forcertain or all interference sensitive operations (e.g., the subframesidentified by a restricted measurement pattern configured for wirelesscommunication device 20 a), or some combination of the two.Alternatively, in some embodiments, the candidate subframes may dependon an ability of the wireless communication device 20 to handlehigh-interference associated with transmissions in the aggressor celland/or a receiver type for a receiver of wireless communication device20 (e.g., an indication of its ability to handle or mitigate certaintypes of interference). More generally, the candidate subframes mayrepresent any subframes that satisfy a candidate condition that relatesin any suitable manner to transmissions in an aggressor cell during therelevant subframes.

As explained above, in particular embodiments, the timing of therelevant downlink transmissions (e.g., synchronous HARQ transmissions)may be constrained by the timing of related uplink transmissions thathave a fixed timing relationship with the relevant downlinktransmissions. As a result, wireless communication system 10 may use thetiming of the related uplink transmissions to control the timing of therelevant downlink transmissions. In certain embodiments, the downlinktransmission to be protected may be triggered by the receipt of the lastcopy of the associated uplink transmission (or the occurrence of thesubframe in which the last copy should have been received). Thus, byintelligently adjusting the number of consecutive copies of the uplinktransmission that the wireless communication device 20 transmits,wireless communication system 10 may be able to ensure that theresponsive downlink transmission occurs during a protected subframe.More specifically, the radio access nodes in particular embodiments mayuse transmission redundancy features, such as Transmission Time Interval(TTI) bundling, to control the timing of the related uplinktransmission.

TTI bundling allows wireless communication devices 20 to make multipleuplink transmission attempts in consecutive subframes before receivingdownlink HARQ feedback. This may result in improved uplink coverage forcell edge wireless communication devices 20 and reduce the HARQ failureprobability (e.g., by reducing HARQ signaling). Additionally, the use oftransmission redundancy may cause changes in the timing for theresponsive downlink HARQ transmissions as the HARQ transmission istriggered by the timing of the last copy. By intelligently adjusting thenumber of copies of the uplink transmission that are made, the radioaccess node can control the timing of the responsive downlink HARQtransmission.

FIGS. 5A and 5B illustrate example timing for HARQ signaling without TTIbundling and with TTI bundling, respectively. In the example of FIG. 5B,a wireless communication device 20 transmits a TTI bundle that includes4 redundancy versions (RVs) transmitted in 4 consecutive TTIs. Note thatcompared to FIG. 5A, the retransmission of the TTI bundle is delayed,because the shortest HARQ round trip time (RTT) with the bundle size of4 is 11 ms which cannot be synchronized with the normal HARQ RTT of 8ms. Thus, a period of 16 ms is configured. The time slots in between canbe used for some other transmissions from the relevant wirelesscommunication device 20 or other wireless communication devices 20. AsFIGS. 5A and 5B show, through the selective use of TTI bundling or othertypes of redundant transmissions, radio access nodes can adjust theoverall timing of an uplink transmission and, in turn, the timing of arelated downlink transmission (e.g., a responsive HARQ transmission). Ifa radio access node in a victim cell uses this technique to align therelevant downlink transmission with a candidate subframe for a potentialaggressor cell, the radio access node can make more effective use of theinterference-protected subframes that are available.

For example, returning to FIG. 1A, a first radio access node (in thisexample, base station 32 a) serving an aggressor cell (here, cell 50 a)is assumed to interfere with a victim cell (here, cell 50 b) served by asecond radio access node (here, low-power node 34 a). Low-power node 34a may obtain configuration information identifying a plurality ofcandidate subframes in which low-power node 34 a can expect reducedinterference from transmissions by base station 32 a in the aggressorcell 50 a. The configuration information may represent informationgenerated by low-power node 34 a itself or by another device. As aresult, low-power node 34 a may obtain this information, for example, byretrieving the information from local storage or by receiving theinformation from another element of wireless communication system 10,such as from a coordinating node of access network 30 or from basestation 32 a itself.

The obtained configuration information may indicate the candidatesubframes in any suitable manner, including by explicitly identifyingeach of the candidate subframes, by providing an identifier for apredetermined group of candidate subframes, or by indicating therelevant subframes in any other suitable manner, explicitly orimplicitly. In particular embodiments, the obtained informationrepresents a bitmap providing a bit for each subframe in the configuredradio frame. The value of each bit indicates whether or not thecorresponding subframe is a candidate subframe with respect to therelevant aggressor cell 50 a. Moreover, as noted above, in particularembodiments, the candidate subframes represent all or some of the MBSFNABS subframes configured for the aggressor cell 50 a. Thus the obtainedinformation may be an indication of which subframes are configured asMBSFN ABS subframes, such as an identifier for a predetermined MBSFN ABSpattern.

In particular embodiments, low-power node 34 a may use the obtainedinformation to configure a wireless communication device 20 it serves(e.g., wireless communication device 20 a) to also take advantage of thetransmission pattern of the aggressor cell. This may ensure wirelesscommunication device 20 a performs measurements or performs certainother operations under reduced interference conditions. For instance, aradio access node may communicate to a wireless communication device 20operating in a potential victim cell a time-domain measurement resourcerestriction pattern or some other form of restricted measurement patternthat indicates the candidate subframes or a subset of those subframes.In particular embodiments, such patterns comprise a bit stringindicating restricted (e.g., ABS) and/or unrestricted subframes for oneor multiple aggressor cells expected to interfere with the victim cell.These restricted measurement patterns may be used to configure wirelesscommunication devices 20 to perform signal strength measurements or toperform other predetermined operations during subframes with improvedinterference conditions. The restricted measurement patterns mayrepresent serving-cell patterns for radio link management (RLM) or radioresource management (RRM) measurements, neighbor-cell pattern for RRMmeasurements, serving-cell pattern for channel state information (CSI)measurements and demodulation, or other types of patterns identifyingspecific resources appropriate for performing measurements or otheroperations (e.g., receiving certain downlink transmissions, such asfeedback information).

After low-power node 34 a has obtained the configuration informationindicating the candidate subframes for the aggressor cell, low-powernode 34 a may use the obtained information to ensure that certaindownlink transmissions made by low-power node 34 a are scheduled duringone of the candidate subframes. When a wireless communication device 20served by low-power node 34 a (here, wireless communication device 20 a)requests permission to make an uplink transmission, low-power node 34 amay use the obtained information to determine a number of copies of theuplink transmission wireless communication device 20 a should make toensure that a downlink transmission associated with the uplinktransmission (for purposes of this example, a responsive HARQtransmission) is made during one of the candidate subframes.

Depending on the implementation of the described solution, low-powernode 34 a may determine the number of copies to transmit by determiningwithout constraint an appropriate number of copies to be transmitted orby selecting the number from a limited set of possible options (e.g.,selecting between “one” and “multiple” copies). For instance, particularembodiments of wireless communication system 10 may support TTI bundlingor other redundancy features that, when activated, provide for a fixedand predetermined number of copies to be transmitted by wirelesscommunication device 20 a. For example, conventional LTE networkssupport a fixed TTI bundle size of 4 copies. In such networks, awireless communication device 20 transmits one copy whenever TTIbundling is not activated and 4 copies whenever TTI bundling isactivated. Thus, in particular embodiments, determining the number ofcopies to be transmitted may represent deciding whether or not toactivate TTI bundling, and a fixed number of copies may be transmittedwhenever TTI bundling is activated.

In certain embodiments, low-power node 34 a may have some schedulingflexibility and may also select the subframe in which wirelesscommunication device 20 a is to transmit the initial copy of the uplinktransmission. In such embodiments, low-power node 34 a may select boththe number of copies to be transmitted and the scheduled subframe forthe first copy to ensure that the responsive downlink subframe is madeduring one of the candidate subframes. In other embodiments, thescheduling request transmitted by wireless communication device 20 a maypertain to a particular subframe (e.g., the subframe occurring apredetermined amount of time after the scheduling request is received),and low-power node 34 a may be required to schedule the first copyduring the relevant subframe. As a result, in such embodiments,low-power node 34 a is unable to adjust the scheduling of the firstcopy, but may be able to ensure the related downlink transmission occursduring a candidate subframe solely by adjusting the number of copies ofthe uplink transmission that are transmitted. After low-power node 34 ahas determined the appropriate number of copies for wirelesscommunication device 20 a to transmit, low-power node 34 a may transmitto wireless communication device 20 a information indicating thatwireless communication device 20 a has been scheduled to transmit anuplink transmission. For example, in particular embodiments, low-powernode 34 a may transmit a scheduling grant that grants wirelesscommunication device 20 a use of transmission resources to make theuplink transmission. Along with this scheduling grant, low-power node 34a may transmit additional scheduling information indicating to wirelesscommunication device 20 a the determined number of copies of the uplinktransmission it should transmit in consecutive subframes. As oneexample, in particular embodiments, wireless communication system 10 maybe able to utilize TTI bundling features to configure a wirelesscommunication device 20 to transmit redundant copies of an uplinktransmission and the scheduling information identifies a specificTTI-bundling configuration (e.g., activate/deactivate TTI bundling; useTTI bundling with a particular bundle size). The scheduling informationmay also configure other aspects of the uplink transmission. Forexample, low-power node 34 a may set a maximum number of retransmissionsthat wireless communication device 20 should send.

Additionally, low-power node 34 a may transmit to base station 32 a orthe radio access node serving another aggressor cell informationindicating the subframes to be protected. The relevant radio access nodemay adjust a transmission pattern (e.g., an ABS MBSFN pattern) for anaggressor cell to ensure the downlink transmissions in victim cell 50 bare protected. Low-power node 34 a may also transmit to and receive fromother radio access nodes information indicating a capability for usingredundant uplink transmissions (e.g., TTI bundling) adaptively to thecandidate subframes and/or a capability to simultaneously supportredundant uplink transmissions and restricted measurement patterns.

Upon receiving the scheduling grant and any additional schedulinginformation (e.g., an indication that bundling should be activated, anexplicit indication of the determined number of copies), wirelesscommunication device 20 a transmits the uplink transmission to low-powernode 34 a. If the configuration information indicates that wirelesscommunication device 20 a should transmit more than one copy of theuplink transmission, wireless communication device 20 a repeats theuplink transmission in subsequent subframes until wireless communicationdevice 20 a has transmitted the determined number of copies of theuplink transmission in consecutive subframes. For example, in particularembodiments, the scheduling information may indicate that wirelesscommunication device 20 a should activate TTI bundling and wirelesscommunication device 20 a may transmit a predetermined number of copiesof the uplink transmission that has been fixed for TTI bundling withinwireless communication system 10.

After wireless communication device 20 a completes transmission of theappropriate number of copies of the uplink transmission, low-power node34 a transmits a downlink transmission related to the uplinktransmission. As explained above, the associated downlink transmissionis related in time to the uplink transmission. Thus, low-power node 34 atimes the downlink transmission in accordance with the timingrelationship between the uplink transmission and its associated downlinktransmission. For example, in particular embodiments, the downlinktransmission represents a HARQ feedback transmission (e.g., ACK or NAK)that should be transmitted a predetermined number of subframes after thelast copy of the uplink transmission is transmitted. Thus, low-powernode 34 a transmits the HARQ feedback transmission a predeterminednumber of subframes after receiving the last copy of the uplinktransmission (or a predetermined number of subframes after the last copyof the uplink transmission should have been received).

Because the number of copies that wireless communication device 20 awould transmit was determined based on the timing of candidatesubframes, the downlink transmission will occur during one of thecandidate subframes. This means that the candidate subframe receivesprotection from interference from the aggressor cell 50 a correspondingto the candidate subframe, resulting in signal timing similar to FIG. 6.In the illustrated example of FIG. 1A, the relevant candidate subframesrelate to the transmissions of base station 32 a in the aggressor cell50 a. As a result, the downlink transmission is protected frominterference due to transmissions by base station 32 a in the aggressorcell 50 a. This protection may result in a greater likelihood thatwireless communication device 20 a will successfully receive thedownlink transmission than if the timing of the downlink transmissionwere left unconstrained.

While the described techniques may be applied unconditionally to protectall downlink transmissions of the relevant types, some embodiments mayutilize these techniques only under certain circumstances. Under othercircumstances, the number of copies set for the corresponding uplinktransmission will be determined using some other default technique, suchas the conventional process for activating TTI bundling. For instance,in particular embodiments, the radio access node in a victim cell maydetermine whether interference conditions warrant applying thetechniques described above before doing so. Thus, in such embodiments,the radio access node may adjust the number of copies that aretransmitted of a particular uplink transmission in response todetermining that a particular interference condition is satisfied. Thisinterference condition may relate in any appropriate manner to theinterference experienced by the relevant wireless communication device20 and/or the victim cell. Additionally, in embodiments that utilize aninterference condition, the interference condition may be the same as acandidate condition that defines the group of candidate subframes (orcandidate resources).

As one example, radio access nodes may be configured to utilize theabove techniques only when interference in a victim cell is determinedto be sufficiently great. Thus, in particular embodiments, theinterference condition may relate to an interference measurementperformed by the radio access node, the relevant wireless communicationdevice 20, or other elements of wireless communication system 10. Theseinterference measurements may represent signal or channel qualityestimates, signal strength measurements, channel estimate reports, orany other suitable measurements of interference and/or signal quality inthe victim cell. In such embodiments, the radio access node maydetermine based on one or more interference measurements whether or notto adjust the number of transmitted copies for a particular uplinktransmission, as described above, to ensure the transmission isprotected.

As another example, wireless communication system 10 may be configuredto utilize the above techniques to reduce the impact of CSG radio accessnodes on wireless communication devices 20 that do not belong to theirsubscriber group, such as in the scenario illustrated by FIG. 1B. Thus,the interference condition may relate to whether the relevant wirelesscommunication device 20 (such as wireless communication device 20 g inFIG. 1B) is operating in a CSG cell for a closed subscriber group towhich the wireless communication device 20 g does not belong. In suchembodiments, a first radio access node (e.g., base station 32 g in FIG.1B) may determine whether or not to adjust the number of transmittedcopies for a particular uplink transmission based on whether wirelesscommunication device 20 g is operating within a cell of a second radioaccess node (e.g., cell 50 g served by low-power node 34 g) that servesa closed subscriber group to which the wireless communication device 20does not belong.

As yet another example, wireless communication system 10 may beconfigured to utilize the above techniques to reduce interference forwireless communication devices 20 operating in cell range expansionzones, such as in the scenario illustrated by FIG. 1C. Thus, inparticular embodiments, the interference condition may relate to whetheror not the relevant wireless communication device 20 (e.g., wirelesscommunication device 20 k in FIG. 1C) is operating in a CRE zone 52 oranother area in which the serving radio access node is expected to havereduced signal strength. In such embodiments, a first radio access node(e.g., low-power node 34 k in FIG. 1C) may determine whether or not toadjust the number of transmitted copies for a particular uplinktransmission based on whether wireless communication device 20 k isoperating within a CRE cell 52 of that radio access node (e.g., CRE zone52 k). This may result in protection for downlink transmissions inareas, like CRE zones, where the victim cell is weaker and may be moresusceptible to interference from an aggressor cell.

In yet other embodiments, the decision of whether or not to useredundant uplink transmissions to facilitate protection of relateddownlink transmissions may be based on other factors that may or may notbe directly related to interference, such as whether the relevantwireless communication device 20 has detected a low-power node 34nearby, how far the relevant wireless communication device 20 is fromits nearest low-power node 34, whether the relevant wirelesscommunication device 20 is capable of supporting redundant transmissions(e.g., TTI bundling capability), whether the relevant wirelesscommunication device 20 has a measurement pattern configured, whetherthe MBSFN ABS pattern in a particular aggressor cell can be configuredto match a round trip time for HARQ in the victim cell without usingredundant transmissions, whether redundant transmissions have beenrequested by another network node (e.g., a self-organizing network(SON), an operations and maintenance (O&M) node, a neighbor radio accessnode), and/or any other suitable considerations.

Although the description above focuses on specific embodiments thatutilize MBSFN ABS subframes of an aggressor cell as the candidatesubframes, the candidate subframes may represent subframes that satisfyany suitable predetermined candidate condition. In certain embodiments,this candidate condition may relate to the amount of interference thatwill occur during the relevant subframe caused by transmissions from oneor more other radio access nodes. In particular, the candidate conditionmay relate to whether or not a specific radio access node or group ofradio access nodes is configured to transmit during that subframe.Similarly, although the description above focuses on specificembodiments that focuses on specific types of related uplink anddownlink transmissions, the described techniques can be used to protectany downlink transmissions that are related in time to an uplinktransmission for which a radio access node can control the redundancy.Thus, transmissions on other downlink control channels, for example,that are triggered by uplink transmissions may also be protected in thedescribed manner.

By selectively using redundant uplink transmissions, particularembodiments of wireless communication system 10 may be able to aligncertain critical downlink transmissions with protected subframesconfigured in aggressor cells. This may result in reduced interferenceand greater reliability in the relevant downlink transmissions and mayreduce the overhead resulting from excessive retransmissions. Thus,certain embodiments of wireless communication system 10 may providenumerous operational benefits. Nonetheless, specific individualembodiments of wireless communication system 10 may provide some, none,or all of these benefits.

FIG. 6 shows an example of how selective redundancy can be used toprotect downlink transmissions. More specifically, FIG. 6 illustrates anexample embodiment in which a radio access node utilizes TTI bundling todelay HARQ feedback for purposes of aligning HARQ feedback transmissionswith a set of candidate subframes. In the example embodiment, a set TTIbundle size of 4 TTI is used and the maximum transmission number is setto 3. With this example configuration, a wireless communication device20 can be scheduled in the (1,0) subframe, and the feedback information(e.g., ACK/NAK) will be transmitted in the (2,1) and (8,2) subframes, asshown. (Here, (u,v) denotes the uth subframe of the vth radio frame.)

In this example embodiment, the pre-defined feasible subset of candidatetime- and/or frequency resources for downlink transmissions includesubframes marked as “MBSFN conf.” in FIG. 6 (which areMBSFN-configurable subframes in the aggressor cell which may use anMBSFN ABS pattern). The subframes in which low-interference conditionsare needed or desirable in the victim cell are marked as “SF to beprotected.” The subframes in which the downlink transmissions will occurare marked as “DL control,” and the subframe for the bundled uplinktransmissions triggering those downlink transmissions are marked as “ULtransmission” in FIG. 6. (In particular embodiments, only a subset ofthe candidate subframes are used to protect the DL control transmissionsand, in such embodiments, the subframes marked “DL control” may differfrom those marked “SF to be protected.”) In this example, without usingTTI bundling adaptively to MBSFN-configurable subframes, “SF to beprotected” would not be a subset of the MBSFN-configurable subframes,which would result in PHICH detection problem and thus HARQ performanceissues. A comparison to the example of FIG. 4 shows that, by usingtransmission redundancy as in FIG. 6, MBSFN ABS subframes can be used toprotect downlink transmissions that it would otherwise not be possibleto protect in this manner.

FIG. 7 is a flow chart illustrating example operation for a radio accessnode, such as one of the base stations 32 or low-power nodes 34 in FIG.1A, in configuring the use of redundant uplink transmissions to protectrelated downlink transmissions. The steps illustrated in FIG. 7 may becombined, modified, or deleted where appropriate. Additional steps mayalso be added to the example operation. Furthermore, the described stepsmay be performed in any suitable order.

Operation begins in FIG. 7 with a radio access node (in this example,low-power node 34 a of FIG. 1A) obtaining configuration informationindicating a plurality of candidate subframes for downlink transmissionsto a wireless communication device 20 (in this example, wirelesscommunication device 20 a) in a first cell at step 700. The candidatesubframes represent subframes that satisfy a predetermined candidatecondition that relates to transmissions in a second cell during therelevant subframe. In particular embodiments, the candidate conditionspecifically relates to an amount of interference that will occur duringthe relevant subframe caused by transmissions in the second cell.

In particular embodiments, low-power node 34 a may generate ameasurement pattern for wireless communication device 20 a based on thecandidate subframes associated with the second cell. The measurementpattern may indicate all or a subset subframe of the candidatesubframes. Wireless communication device 20 a may be configured toperform certain measurements or receive certain transmissions in thesubframes indicated by the measurement pattern. Thus, in the illustratedexample, low-power node 34 a generates a measurement pattern thatindicates all the candidate subframes for the second cell and transmitsthat measurement pattern to wireless communication device 20 a, at step702.

Additionally, low-power node 34 a may transmit to another radio accessnode, such as the radio access node serving the second cell (e.g., basestation 32 a), information indicating one or more of the candidatesubframes that low-power node 34 a will use for downlink transmissions,the determined number of copies of the uplink transmission, and/or otherinformation that will allow the other radio access node to coordinateits transmissions to protect the downlink transmissions made bylow-power node 34 a. Thus, in the illustrated example, low-power node 34a transmits coordination information to base station 32 a at step 704.For example, in particular embodiments, the configuration informationreceived by low-power node 34 a initially may identify potentialprotected subframes (e.g., subframes that could be configured for MBSFNABS). Base station 32 a may use the coordination information todetermine which of the potential protected subframes actually need to beprotected. This may allow wireless communication system 10 to limit howmuch coordination will constrain the aggressor cell's use oftransmission resources.

With the configuration information, low-power node 34 a may be able tobegin configuring uplink transmissions by wireless communication device20 a based on the configuration information. In particular embodiments,this configuration may be initiated by wireless communication device 20a indicating it has data available for transmission. For example, in theillustrated embodiment, low-power node 34 a receives a schedulingrequest from wireless communication device 20 a requesting thatlow-power node 34 a schedule an uplink transmission for wirelesscommunication device 20 a, at step 706.

In particular embodiments, radio access nodes of wireless communicationsystem 10 may not attempt to protect its downlink transmissions underall circumstances. Instead, the radio access nodes may only configurewireless communication devices 20 to facilitate protection in certainsituations, such as based on the interference the relevant wirelesscommunication device 20 is experiencing or is expected to experience.Thus, in the illustrated example, low-power node 34 a determines whetheran interference condition is satisfied at step 708. This interferencecondition may relate to actual interference measurements, to whetherwireless communication device 20 a is located within a cell serving aCSG to which wireless communication device 20 a does not, to whether thewireless communication device 20 a is operating within a cell rangeexpansion zone, or to any other consideration that affects theinterference or anticipated interference experienced by wirelesscommunication device 20 a.

If the interference condition is not satisfied, low-power node 34 mayconfigure wireless communication device 20 a to transmit a single copyof the relevant uplink transmission or use conventional techniques todetermine whether redundancy should be applied. In the illustratedexample, however, it is assumed that the interference condition issatisfied and operation continues to step 710. As noted above, the stepsof FIG. 7 may be performed in any suitable order in various embodiments.Thus, although shown as not occurring until step 708 in the illustratedexample, the completion any of the preceding steps may, in alternativeembodiments, also be conditioned on this determination of whether aninterference condition is satisfied.

At step 710, low-power node 34 a determines, based on the informationregarding the candidate subframes, a number of copies of an uplinktransmission that wireless communication device 20 a should transmit inconsecutive uplink subframes. Specifically, low-power node 34 a selectsa number of copies that will result in a downlink transmission relatedto the uplink transmission occurring during one of the candidatesubframes. As explained above, depending on the implementation of thedescribed solution, low-power node 34 a may determine the number ofcopies to transmit by determining without constraint an appropriatenumber of copies to be transmitted or by selecting the number from alimited set of possible options (e.g., selecting between “one” and“multiple” copies). For instance, in particular embodiments, determiningthe number of copies to be transmitted may represent low-power node 34deciding whether or not to activate TTI bundling, and a fixed number ofcopies (e.g., 4 copies) may be transmitted whenever TTI bundling isactivated.

At step 712, low-power node 34 a then configures the wirelesscommunication device 20 a to transmit the determined number of copies ofthe uplink transmission in consecutive subframes. In particularembodiments, low-power node 34 a configures wireless communicationdevice 20 a to transmit the determined number of copies of the uplinktransmission by transmitting scheduling information or other types ofinstructions to wireless communication device 20 a indicating directlyor indirectly the number of copies of the uplink transmission totransmit. In particular embodiments, this scheduling information mayexplicitly specify the number of copies wireless communication device 20a should transmit. As noted above, in particular embodiments, ratherthan explicitly specifying a number of copies, this configurationinformation may indicate whether or not wireless communication device 20a should activate TTI bundling or some other form of redundancy underwhich wireless communication device 20 a transmits a fixed number ofcopies.

Once wireless communication device 20 a receives the schedulinginformation indicating the number of copies of the uplink transmissionto transmit or is otherwise configured by low-power node 34 a totransmit the appropriate number of copies, wireless communication device20 may perform the relevant uplink transmission. In doing so, wirelesscommunication device 20 a transmits, in consecutive subframes, thenumber of copies of the uplink transmission determined by low-power node34 a. Thus, at step 714, low-power node 34 a receives one or more copiesof an uplink transmission transmitted by wireless communication device20 a.

In particular embodiments, low-power node 34 a transmits a downlinktransmission related to the uplink transmission with a timing thatsatisfies a predetermined relationship to the timing of the uplinktransmission. For example, low-power node 34 a may transmit feedbackinformation (e.g., HARQ feedback comprising an ACK/NACK bit). In certainembodiments, the timing relationship results in the downlinktransmission occurring in a subframe that is a fixed number of subframesafter the last copy of the uplink transmission is received or isscheduled to be received. Consequently, in the illustrated embodiment,low-power node 34 a transmits the downlink transmission a predeterminedamount of time after a last of the one or more copies is received, atstep 716. Because of the manner in which low-power node 34 a determinedthe number of copies of the uplink transmission to be transmitted, thesubframe occurring the predetermined amount of time after the last copyis received is one of the candidate subframes. Thus, the downlinktransmission made by low-power node 34 occurs during a candidatesubframe, and the downlink transmission is protected from theinterference of the second cell as a result. Operation of low-power node34 a with respect to configuring the relevant uplink transmission maythen end as shown in FIG. 7.

In addition to or as an alternative to using redundant uplinktransmissions to facilitate protection of downlink transmissions,wireless communication system 10 may utilize other forms of coordinationbetween its radio access nodes to partially or fully protect downlinktransmissions in potential victim cells from interference by potentialaggressor cells. FIG. 8 illustrates an example embodiment of wirelesscommunication system 10 in which one or more radio access nodes servingdifferent cells 50 coordinate their configuration of those cells 50 toprotect downlink transmissions in some or all of the relevant cells 50.The techniques illustrated in the example embodiment may be used inconjunction with the uplink redundancy solutions described above or asseparate standalone solutions for protecting downlink transmissions.

In the example embodiment, a first radio access node (in this example,low-power node 34 x) transmits coordination information to a secondaccess node (here, base station 32 z). The configuration information(represented by “configuration information message 80” in FIG. 8)indicates a group of one or more subframes in which low-power node 34 xwill transmit feedback information to a wireless communication device 20(here, wireless communication device 20 a) in a victim cell served bylow-power node 34 x (here, cell 50 x). Low-power node 34 x may transmitthe coordination information to base station 32 z using a dedicatedinterface 82 (e.g., an X2 interface) as shown in FIG. 8 or using anysuitable direct or indirect connection between the components.

Based on the coordination information, base station 32 z determines asecond group of one or more time and/or frequency transmission resourcesto use in an aggressor cell served by base station 32 z (here, cell 50z). These time and/or frequency resources (referred to generically inthis description as “transmission resources”) may represent timeresources (e.g., subframes) or frequency resources (e.g., subcarriers)or a combination of both (e.g., use of specific subcarriers during aparticular subframe. Base station 32 z determines the second group oftransmission resources so as to prevent or limit overlap between thesecond group and the first group. Thus, the second group of transmissionresources differs at least in part from the first group. Base station 32z then configures itself to transmit feedback information to one or morewireless communication devices 20 using the second group oftransmissions resources.

Depending on the specific embodiment of wireless communication system10, base station 32 z may achieve the configuration in a variety ofdifferent ways. In particular embodiments, the configuration process mayinvolve adjusting the time and/or frequency resources used by basestation 32 z, in general or for certain specific transmissions, in theaggressor cell 50 z to ensure that the transmission resources used bybase station 32 z are not identical in time and frequency with those tobe used by low-power node 34 x in the victim cell 50 x.

In particular embodiments of wireless communication system 10, basestation 32 z may adjust the transmission resources that base station 32z uses to transmit the same type of downlink transmissions that are tobe protected in the victim cell 50 x. For instance, in embodiments inwhich downlink PHICH transmissions are to be protected, base station 32z may adjust parameters associated with base station 32 z that affectthe transmission resources that base station 32 z uses to transmit itsown PHICH transmissions. For example, base station 32 z may adjust suchparameters as a cell identifier associated with base station 32 z, anumber of modulation symbols (e.g., OFDM symbols in LTE embodiments)used by base station 32 z for the relevant transmissions, or a groupnumber (e.g., a PHICH group number) associated with the relevanttransmissions in the aggressor cell 50 z.

In particular embodiments, base station 32 z may adjust the transmissionresources used for the relevant transmissions by selecting orreselecting parameters associated with some or all of the wirelesscommunication devices 20 served by the aggressor cell 50 z. For example,base station 32 z may select or reselect a cyclic shift or resourceallocation used by one or more wireless communication device(s) 20served by the aggressor cell 50 z to ensure that the relevant downlinktransmissions in the aggressor cell 50 z do not use the transmissionresources indicated by the receive configuration information. In suchcases, base station 32 z may transmit information indicating the newlyselected parameters to the relevant wireless communication device(s) 20(e.g., wireless communication device 20 y in FIG. 8).

Furthermore, in particular embodiments, base station 32 z may alsoadjust the transmission resources it uses for other types of downlinktransmissions that are different from the downlink transmissions to beprotected in the victim cell 50 x. For example, in embodiments in whichPHICH transmissions are to be protected in the victim cell 50 x, basestation 32 z may nonetheless adjust the transmission resources used totransmit other channels, such as the PDCCH, to ensure those channels donot interfere with the protected transmissions. Thus, in suchembodiments, base station 32 z may select or reselect an identifierassigned to one or more wireless communication devices 20 (e.g., aC-RNTI) served by the aggressor cell 50 z, a transmission format fortransmissions on the relevant channel (e.g., a number of control channelelements (CCE) to be used), or any other suitable parameter to ensurethat the transmission resources used for the relevant downlinktransmissions in the aggressor cell 50 z do not coincide with thetransmission resources identified by the received coordinationinformation.

Depending on the embodiment of wireless communication system 10, basestation 32 z may initiate the described coordination procedure in avariety of different ways. In particular embodiments, base station 32 zmay initiate the coordination procedure autonomously (e.g., based oninterference measurements in the victim cell 50 x), in response toexplicit signaling from the other node, based on a pre-defined rule forcoordinating the behavior of radio network nodes, in response toinstructions from a coordinating node responsible for coordinatingoperation of radio access nodes to protect transmissions, and/or as aresult of any suitable other triggering event.

FIG. 9 is a flow chart illustrating example operation of a radio accessnode, such as one of the base stations 32 or low-power nodes 34 in FIG.8, in coordinating configuration with another radio access node toprotect downlink transmissions made by one or both of the radio accessnodes. The steps illustrated in FIG. 9 may be combined, modified, ordeleted where appropriate. Additional steps may also be added to theexample operation. Furthermore, the described steps may be performed inany suitable order.

Operation begins in FIG. 9, at step 900, with a radio access node (inthis example, base station 32 z of FIG. 8) obtaining coordinationinformation indicating a plurality of candidate subframes for downlinktransmissions to a wireless communication device 20 in a first cell atstep 900. The candidate subframes represent subframes in which anotherradio access node (in this example, low-power node 34 x) will transmitfeedback information (e.g., HARQ ACK/NACK bits) to one or more wirelesscommunication devices 20 served by low-power node 34 x (in this example,wireless communication device 20 x).

Base station 32 z then determines based on the obtained coordinationinformation a second group of transmission resources base station 32 zshould use to transmit feedback information to a wireless communicationdevice 20 x served by base station 32 z, at step 902. The second groupof subframes differs from the first group of subframes.

Base station 32 z then proceeds to configure itself to transmit feedbackinformation to a wireless communication device 20 served by base station32 z (e.g., wireless communication device 20 y) using the second groupof transmission resources at step 904. Base station 32 z can configureitself to transmit feedback information using the second group ofresources in a variety of ways. As one example, base station 32 z mayadjust the transmission resources used for the feedback channel bysetting a cell identifier for base station 32 z. As another example,base station 32 z may adjust the transmission resources used for thefeedback channel by setting a number of modulation symbols (e.g., OFDMsymbols) to be used per subframe by the base station 32 z. As anotherexample, base station 32 z may adjust the transmission resources usedfor the feedback channel by setting a group number of wirelesscommunication device 20 y. The group number indicates a set oftransmission resources used to transmit the feedback information. As yetanother example, base station 32 z may adjust the transmission resourcesused for the feedback channel by setting a cyclic shift associated witha demodulation reference signal transmitted by wireless communicationdevice 20 y.

In addition to or as an alternative to configuring a downlink feedbackchannel, such as a PHICH channel, base station 32 z may configure otherdownlink channels to coordinate its downlink transmissions with those oflow-power node 34 x, at step 906. For example, base station 32 z mayadjust the transmission resources of a control channel such as the PDCCHby allocating an identifier (e.g., a C-RNTI) for wireless communicationdevice 20 y that affects the resource mapping for downlink transmissionsto wireless communication device 20 y on the relevant channel. Asanother example, base station 32 z may adjust the transmission resourcesof a control channel such as the PDCCH by adjusting a transmissionformat for the control channel (e.g., setting a number control channelelements to be used)).

After configuring itself based on the coordination information, basestation 32 z then transmits downlink transmissions in accordance withthe configuration at step 908. As a result of the coordination, thedownlink transmissions transmitted by base station 32 z will notinterfere with the feedback information transmitted by low-power node 34x. Operation of base station 32 z with respect to coordinatingtransmissions with low-power node 34 x may then end as shown in FIG. 9.

FIG. 10 is a block diagram illustrating in greater detail the contentsof a particular embodiment of a radio access node 1000 that may beconfigured to protect downlink transmissions in a cell it is serving(when operating in a potential victim cell) and/or in a nearby cellserved by another radio access node (when operating in a potentialaggressor cell). Particular embodiments of the example radio access node1000 may be capable of scheduling redundant uplink transmissions toprotect related downlink transmissions as described above, for example,with respect to FIG. 7. Particular embodiments of the example radioaccess node 1000 may additionally or alternatively be capable ofcoordinating its downlink transmissions with those of another cell asdescribed above, for example, with respect to FIG. 9. As shown in FIG.10, the example embodiment of network node 1000 includes a nodeprocessor 1002, a node memory 1004, a communication interface 1006, anantenna 1008, a transmitter 1010, and a receiver 1012.

Node processor 1002 may represent or include any form of processingcomponent, including dedicated microprocessors, general-purposecomputers, or other forms of electronic circuitry capable of processingelectronic information. Examples of node processor 1002 includefield-programmable gate arrays (FPGAs), programmable microprocessors,digital signal processors (DSPs), application-specific integratedcircuits (ASICs), and any other suitable specific- or general-purposeprocessors. Although FIG. 10 illustrates, for the sake of simplicity, anembodiment of network node 1000 that includes a single node processor1002, network node 1000 may include any number of node processors 1002configured to interoperate in any appropriate manner.

Node memory 1004 stores configuration information obtained by radioaccess node 1000. Node memory 1004 may also store processor instructionsfor node processor 1002, coding algorithms, transmission parameters,and/or any other data utilized by radio access node 1000 duringoperation. Node memory 1004 may comprise any collection and arrangementof volatile or non-volatile, local or remote devices suitable forstoring data, such as random access memory (RAM), read only memory(ROM), magnetic storage, optical storage, or any other suitable type ofdata storage components. Although shown as a single element in FIG. 10,node memory 1004 may include one or more physical components local to orremote from radio access node 1000.

Communication interface 1006 comprises electronic circuitry and othercomponents suitable to permit radio access node 1000 to communicate withother radio access nodes and/or other elements of access network 30 andcore network 40. For example, in embodiments in which radio access node1000 exchanges coordination information with other network nodes inaccess network 30, communication interface 1006 may represent circuitrycapable of communicating over an X2 interface between radio access node1000 and other nodes of access network 30.

Antenna 1008 represents any suitable conductor capable of receiving andtransmitting wireless signals. Transmitter 1010 transmits radiofrequency(RF) signals over antenna 1008, and receiver 1012 receives from antenna1008 RF certain signals transmitted by wireless communication devices20. Although the example embodiment in FIG. 10 includes certain numbersand configurations of antennas, receivers, and transmitters, alternativeembodiments of radio access node 1000 may include any suitable number ofthese components. Additionally, transmitter 1010, receiver 1012, and/orantenna 1008 may represent, in part or in whole, the same physicalcomponents. For example, particular embodiments of radio access node1000 include a transceiver representing both transmitter 1010 andreceiver 1012.

Although the present invention has been described with severalembodiments, a myriad of changes, variations, alterations,transformations, and modifications may be suggested to one skilled inthe art, and it is intended that the present invention encompass suchchanges, variations, alterations, transformations, and modifications asfall within the scope of the appended claims.

For the avoidance of doubt, the present invention includes the subjectmatter as defined in the following numbered paragraphs (abbreviated“para.”).

Para. 1. A method for configuring communication in a wirelesscommunication system, the method comprising:

obtaining, at a first network node, information indicating a pluralityof candidate subframes for downlink transmissions to a wirelesscommunication device in a first cell served by the first network node,wherein each candidate subframe satisfies a candidate condition thatrelates to transmissions in a second cell during that subframe;

determining, based on the obtained information, a number of copies of anuplink transmission a wireless communication device should transmit inconsecutive uplink subframes so that a downlink transmission related tothe uplink transmission will occur during one of the candidatesubframes; and

configuring the wireless communication device to transmit the determinednumber of copies of the uplink transmission in consecutive subframes.

Para. 2. The method of para. 1, wherein the candidate condition furtherrelates to an amount of interference that will occur during a respectivesubframe caused by transmissions in the second cell.

Para. 3. The method of para. 1 further comprising configuring ameasurement pattern for the wireless communication device, themeasurement pattern indicating one or more subframes in which therelated downlink transmission is to be received by the wirelesscommunications device from the first network node, wherein:

the one or more indicated subframes comprise candidate subframes; and

the downlink transmission related to the uplink transmission will occurduring one or more of the indicated subframes.

Para. 4. The method of para. 1, wherein determining the number of copiesthe wireless communication device should transmit based on the obtainedinformation comprises:

determining that an interference condition is satisfied, wherein theinterference condition relates to an amount of interference experiencedby the wireless communication device; and

in response to determining that the interference condition is satisfied,determining the number of copies based on the obtained information.

Para. 5. The method of para. 4, wherein the interference conditionrelates to an interference measurement performed by the first networknode or the wireless communication device.

Para. 6. The method of para. 4, wherein the interference conditionrelates to whether the wireless communication device is located within acell of a second network node that serves a closed subscriber group towhich the wireless device does not belong.

Para. 7. The method of para. 4, wherein the interference conditionrelates to whether the wireless communication device is operating withina cell range expansion zone of the first cell.

Para. 8. The method of para. 1, wherein the candidate subframes comprisesubframes during which the second cell is configured to use MulticastBroadcast Single Frequency Network (MBSFN) Almost Blank Subframes.

Para. 9. The method of para. 1, wherein the downlink transmissioncomprises feedback information indicating whether the uplinktransmission was successfully received.

Para. 10. The method of para. 9, further comprising:

receiving one or more copies of the uplink transmission; and

transmitting the downlink transmission during one of the candidatesubframes a predetermined amount of time after a last of the one or morecopies is received.

Para. 11. The method of para. 1, further comprising transmittinginformation indicating a candidate subframe to be used for the downlinktransmission to a second network node associated with the identifiedcandidate subframe.

Para. 12. The method of para. 1, further comprising scheduling theuplink transmission based on the received information and the determinednumber of copies so that the downlink transmission will occur in one ofthe candidate subframes.

Para. 13. The method of para. 1, further comprising transmittinginformation indicating a capability of the first network node toadaptively use redundant uplink transmissions to align related downlinktransmissions with candidate subframes.

Para. 14. An apparatus for configuring communication in a wirelesscommunication system, the apparatus comprising:

a transmitter configured to transmit configuration information to awireless communication device; and

a processor configured to:

-   -   obtain, at a first network node, information indicating a        plurality of candidate subframes for a downlink transmission to        a wireless communication device in a first cell, wherein each        candidate subframe satisfies a predetermined candidate condition        that relates to transmissions in a second cell during that        subframe;    -   determine, based on the obtained information, a number of copies        of an uplink transmission a wireless communication device should        transmit a wireless communication device should transmit in        consecutive uplink subframes so that a downlink transmission        related to the uplink transmission will occur during one of the        candidate subframes; and    -   configure the wireless communication device to transmit the        determined number of copies of the uplink transmission in        consecutive subframes.        Para. 15. The apparatus of para. 14, wherein the candidate        condition further relates to an amount of interference that will        occur during a respective subframe caused by transmissions in        the second cell.        Para. 16. The apparatus of para. 14, wherein the processor is        further configured to transmit a measurement pattern to the        wireless communication device, the measurement pattern        indicating one or more subframes in which the related downlink        transmission is to be received by the wireless communication        device from the first network node, wherein

the one or more indicated subframes comprise candidate subframes; and

the downlink transmission related to the uplink transmission will occurduring one or more of the indicated subframes.

Para. 17. The apparatus of para. 14, wherein the processor is configuredto determine the number of copies the wireless communication deviceshould transmit based on the obtained information by:

determining that an interference condition is satisfied, wherein theinterference condition relates to an amount of interference experiencedby the wireless communication device; and

in response to determining that the interference condition is satisfied,determining the number of copies based on the obtained information.

Para. 18. The apparatus of para. 17, wherein the interference conditionrelates to an interference measurement performed by the first networknode or the wireless communication device.

Para. 19. The apparatus of para. 17, wherein the interference conditionrelates to whether the wireless communication device is located within acell of a second network node that serves a closed subscriber group towhich the wireless device does not belong.Para. 20. The apparatus of para. 17, wherein the interference conditionrelates to whether the wireless communication device is operating withina cell range expansion zone of the first cell.Para. 21. The apparatus of para. 14, wherein the candidate subframescomprise subframes during which the second network cell is configured touse Multicast Broadcast Single Frequency Network (MBSFN) Almost BlankSubframes.Para. 22. The apparatus of para. 14, wherein the downlink transmissioncomprises feedback information indicating whether the uplinktransmission was successfully received.Para. 23. The apparatus of para. 22, wherein the processor is furtherconfigured to:

receive one or more copies of the uplink transmission; and

transmit the downlink transmission during one of the candidate subframesa predetermined amount of time after a last of the one or more copies isreceived.

Para. 24. The apparatus of para. 14, wherein the processor is furtherconfigured to transmit information indicating a candidate subframe to beused for the downlink transmission to a second network node associatedwith the identified candidate subframe.

Para. 25. The apparatus of para. 14, wherein the processor is furtherconfigured to schedule the uplink transmission based on the receivedinformation and the determined number of copies so that the downlinktransmission will occur in one of the candidate subframes.Para. 26. The apparatus of para. 14, wherein the processor is furtherconfigured to transmit information indicating a capability to adaptivelyuse redundant uplink transmissions to align related downlinktransmissions with candidate subframes.Para. 27. A method for configuring communication in a wirelesscommunication system, the method comprising:

obtaining information indicating a first group of one or more subframesof a radio frame in which a first network node will transmit feedbackinformation to one or more wireless communication devices served by thefirst network node;

determining, based on the obtained information, a second group of one ormore subframes in which a second network node should transmit feedbackinformation to one or more wireless communication devices served by thesecond network node, wherein the second group of subframes differs fromthe first group of subframes;

configuring the second network node to transmit feedback information toone or more wireless communication devices during the second group ofsubframes; and

transmitting feedback information from the first network node during thesecond group of subframes.

Para. 28. The method of para. 27, wherein the information indicating thefirst group and the second group of one or more subframes is obtained byexplicit signaling from another node, based on a pre-defined rule forcoordinating behavior of radio network nodes, in response toinstructions from a coordinating node responsible for coordinatingoperation of radio access nodes to protect transmissions.Para. 29. The method of para. 27, wherein configuring the second networknode to transmit feedback information during the second group ofsubframes comprises adjusting time and/or frequency resources of afeedback channel transmitted by the second network node by setting acell identifier for the second network node.Para. 30. The method of para. 27, wherein configuring the second networknode to transmit feedback information during the second group ofsubframes comprises adjusting time and/or frequency resources of afeedback channel transmitted by the second network node by setting anumber of orthogonal frequency division modulation symbols (OFDM)symbols to be used per subframe by the second network node.Para. 31. The method of para. 27, further comprising adjusting timeand/or frequency resources of a control channel transmitted by thesecond network node by allocating an identifier to a wirelesscommunication device served by the second network node.Para. 32. The method of para. 27, further comprising adjusting a controlchannel transmitted by the second node by adjusting a transmissionformat for the control channel.Para. 33. The method of para. 27, wherein configuring the second networknode to transmit feedback information during the second group ofsubframes comprises adjusting a group number of a wireless communicationdevice served by the second network node, wherein the group numberindicates a set of transmission resources used to transmit the feedbackinformation.Para. 34. The method of para. 27, wherein configuring the second networknode to transmit feedback information during the second group ofsubframes comprises adjusting a feedback channel transmitted by thesecond network node by setting a cyclic shift associated with ademodulation reference signal transmitted by a wireless communicationdevice served by the second network node.Para. 35. The method of para. 27, wherein the second group of subframescomprise almost blank subframes (ABS).Para. 36. The method of para. 27, wherein transmitting feedbackinformation comprises transmitting Hybrid-Automatic Repeat Request(HARQ) feedback on a Physical HARQ Indicator Channel (PHICH).Para. 37. An apparatus for configuring communication in a wirelesscommunication system, the apparatus comprising:

a transmitter adapted to transmit feedback information to a wirelesscommunication device; and

a processor adapted to:

-   -   obtain information indicating a first group of one or more        subframes of a radio frame in which a first network node will        transmit feedback information to one or more wireless        communication devices served by the first network node;    -   determine, based on the obtained information, a second group of        one or more subframes in which a second network node should        transmit feedback information to one or more wireless        communication devices served by the second network node, wherein        the second group of subframes differs from the first group of        subframes;    -   configure the second network node to transmit feedback        information to one or more wireless communication devices during        the second group of subframes; and    -   transmit feedback information from the first network node during        the second group of subframes.        Para. 38. The apparatus of para. 37, wherein the processor is        operable to obtain the information indicating the first group        and the second group of one or more subframes by explicit        signaling from another node, based on a pre-defined rule for        coordinating behavior of radio network nodes, in response to        instructions from a coordinating node responsible for        coordinating operation of radio access nodes to protect        transmissions.        Para. 39. The apparatus of para. 37, wherein the processor is        adapted to configure the second network node to transmit        feedback information during the second group of subframes by        setting a cell identifier for the second network node.        Para. 40. The apparatus of para. 37, wherein the processor is        adapted to configure the second network node to transmit        feedback information during the second group of subframes by        setting a number of orthogonal frequency division modulation        symbols (OFDM) symbols to be used per subframe by the second        network node.        Para. 41. The apparatus of para. 37, wherein the processor is        further adapted to adjust a timing of a control channel        transmitted by the second network node by allocating an        identifier to a wireless communication device served by the        second network node.        Para. 42. The apparatus of para. 37, wherein the processor is        further adapted to adjust a timing of a control channel        transmitted by the second node by adjusting a transmission        format for the control channel.        Para. 43. The apparatus of para. 37, wherein the processor is        adapted to configure the second network node to transmit        feedback information during the second group of subframes by        adjusting a group number of a wireless communication device        served by the second network node, wherein the group number        indicates a set of transmission resources used to transmit the        feedback information.        Para. 44. The apparatus of para. 37, wherein the processor is        adapted to configure the second network node to transmit        feedback information during the second group of subframes by        setting a cyclic shift associated with a demodulation reference        signal transmitted by a wireless communication device served by        the second network node.        Para. 45. The apparatus of para. 37, wherein the second group of        subframes comprise almost blank subframes (ABS).        Para. 46. The apparatus of para. 37, wherein the processor is        operable to transmit feedback information by transmitting        Hybrid-Automatic Repeat Request (HARQ) feedback on a Physical        HARQ Indicator Channel (PHICH).

What is claimed is:
 1. A method for configuring communication in awireless communication system, the method comprising: obtaininginformation indicating a first group of one or more subframes of a radioframe in which a first network node will transmit feedback informationto one or more wireless communication devices served by the firstnetwork node; determining, based on the obtained information, a secondgroup of one or more subframes in which a second network node shouldtransmit feedback information to one or more wireless communicationdevices served by the second network node, wherein the second group ofsubframes differs from the first group of subframes; configuring thesecond network node to transmit feedback information to one or morewireless communication devices during the second group of subframes; andtransmitting feedback information from the second network node duringthe second group of subframes, wherein configuring the second networknode to transmit feedback information during the second group ofsubframes comprises one of: adjusting time and/or frequency resources ofa feedback channel transmitted by the second network node by setting acell identifier for the second network node or setting a number oforthogonal frequency division modulation symbols (OFDM) symbols to beused per subframe by the second network node, adjusting a group numberof a wireless communication device served by the second network node,wherein the group number indicates a set of transmission resources usedto transmit the feedback information, or adjusting a feedback channeltransmitted by the second network node by setting a cyclic shiftassociated with a demodulation reference signal transmitted by awireless communication device served by the second network node.
 2. Themethod of claim 1, wherein the information indicating the first group ofone or more subframes is obtained by explicit signaling from anothernode, based on a pre-defined rule for coordinating behavior of radionetwork nodes, and/or in response to instructions from a coordinatingnode responsible for coordinating operation of radio access nodes toprotect transmissions.
 3. The method of claim 1, further comprisingadjusting time and/or frequency resources of a control channeltransmitted by the second network node by allocating an identifier to awireless communication device served by the second network node.
 4. Themethod of claim 1, further comprising adjusting a control channeltransmitted by the second node by adjusting a transmission format forthe control channel.
 5. The method of claim 1, wherein the second groupof subframes comprise almost blank subframes, ABS.
 6. The method ofclaim 1, wherein transmitting feedback information comprisestransmitting Hybrid-Automatic Repeat Request, HARQ, feedback on aPhysical HARQ Indicator Channel, PHICH.
 7. An apparatus for configuringcommunication in a wireless communication system, the apparatuscomprising: a transmitter adapted to transmit feedback information to awireless communication device; and a processor adapted to: obtaininformation indicating a first group of one or more subframes of a radioframe in which a first network node will transmit feedback informationto one or more wireless communication devices served by the firstnetwork node; determine, based on the obtained information, a secondgroup of one or more subframes in which a second network node shouldtransmit feedback information to one or more wireless communicationdevices served by the second network node, wherein the second group ofsubframes differs from the first group of subframes; configure thesecond network node to transmit feedback information to one or morewireless communication devices during the second group of subframes; andtransmit feedback information from the second network node during thesecond group of subframes, wherein the processor is adapted to configurethe second network node to transmit feedback information during thesecond group of subframes by one of: adjusting time and/or frequencyresources of a feedback channel transmitted by the second network nodeby setting a cell identifier for the second network node or setting anumber of orthogonal frequency division modulation symbols (OFDM)symbols to be used per subframe by the second network node, adjusting agroup number of a wireless communication device served by the secondnetwork node, wherein the group number indicates a set of transmissionresources used to transmit the feedback information, or adjusting afeedback channel transmitted by the second network node by setting acyclic shift associated with a demodulation reference signal transmittedby a wireless communication device served by the second network node. 8.The apparatus of claim 7, wherein the processor is operable to obtainthe information indicating the first group of one or more subframes byexplicit signaling from another node, based on a pre-defined rule forcoordinating behavior of radio network nodes, and/or in response toinstructions from a coordinating node responsible for coordinatingoperation of radio access nodes to protect transmissions.
 9. Theapparatus of claim 7, wherein the processor is further adapted to adjusta timing of a control channel transmitted by the second network node by:allocating an identifier to a wireless communication device served bythe second network node; or adjusting a transmission format for thecontrol channel.
 10. The apparatus of claim 7, wherein the second groupof subframes comprise almost blank subframes, ABS.
 11. The apparatus ofclaim 7, wherein the processor is operable to transmit feedbackinformation by transmitting Hybrid-Automatic Repeat Request, HARQ,feedback on a Physical HARQ Indicator Channel, PHICH.